A lot of water and wastewater gets moved around in municipal systems. As water gets pumped, treated, used, moved, treated, recycled, and returned to the earth, there are many different points when we need to know how much we have in a basin, tank, well, etc. If a tank is already full of water, we need to either stop pumping into it or pump some out. The key piece to this is the level control indicator.
There are a lot of different kinds of level control instruments. Below is not an exhaustive list, but we thought it'd be useful to put together a quick reference for level control options. Here's a few of the most common level control indicators we see.
There are a lot of different kinds of level control instruments. Below is not an exhaustive list, but we thought it'd be useful to put together a quick reference for level control options. Here's a few of the most common level control indicators we see.
Float switches
- Spherical shape.
- When the water reaches the float switch, the contact on the float signals that it has reached that level.
- On/off control - the water is either at that point or not, making this type less precise than other options.
- In trends, the level would information looks like a bar graph.
- If used as primary level control, 4-5 floats are used.
- Often used as a backup level control system with 2 floats (high and low level).
- Often higher maintenance due to grease build up.
- Inexpensive
Level Probes
- Stick like shape.
- Contacts spaced out on probe. When water reaches the contact, it signals that the water has reached that level.
- Comes in many different sizes and different amount of contacts on a probe.
- On/off control - the water is either at that point or not, making this type less precise than other options.
- In trends, the level information looks like a bar graph.
Submersible Pressure Transducers
- Sensor submerged at botton of wet well.
- Great for use in lift stations.
- Comes in different pressure sizes, such as 0-5 psi or 0-10 psi. The top psi value relates to the maximum amount of water that could be in the tank.
- Gives 4-20 mA range, so very precise.
- In trends, the level information looks like a line graph/smooth line.
Pressure Transmitters
- Sensor mounted in pressure line.
- Commonly used in water systems.
- Comes in different pressure sizes, such as 0-5 psi or 0-10 psi. The top psi value relates to the maximum amount of water that could be in the tank.
- Gives 4-20 mA range, so very precise.
- In trends, the level information looks like a line graph/smooth line.
Ultrasonic transducers
- Sensor mounted from above liquid and uses ultrasonic signal to tell level.
- Good in applications where submerged sensor not an option.
- Gives 4-20 mA range, so very precise.
- In trends, the level information looks like a line graph/smooth line.
- Watch out for foam affecting readings.
